The present invention relates to calibration mechanisms for pressure switches, and more particularly, to an improved arrangement for stopping or limiting cam rotation.
The invention is particularly applicable to pressure switches for use in controlling the water-fill level of various appliances such as washing machines and dishwashers, and will be described in connection therewith. However, it will be appreciated by those skilled in the art that the invention may be used advantageously in any calibration mechanism of the type having a rotatable cam member and a movable cam follower for selecting among a range of actuation to be sensed by the associated mechanism.
In typical prior art actuating mechanisms, the cam profiles have been provided with projecting portions on either side of the portion of the cam profile which corresponds to the pressure level settings between the normal low and normal high. These projections have been employed as cam stops to limit rotation of the cam in either direction. The cam stop arrangement is especially important as it relates to the cam positions corresponding to a pressure level setting in excess of the normal high setting. The reason is that in a typical pressure switch mechanism, an excessively high pressure setting will result in flooding because even a full tube of water will not exert sufficient pressure on the pressure switch diaphragm to activate the switch, shutting off the flow of water.
Several examples of conventional prior art cam profiles, utilizing projecting portions as stops, are illustrated in U.S. Pat. Nos. 2,934,618 and 3,230,328. One problem associated with the use of such projections has been the tendency of the projections to engage and become entangled with the lead wires during the rotation of the cam. When this occurs, it is quite possible for a lead wire to be pulled loose from its terminal, interfering with the electrical circuitry which shuts off the water-full function, and causing flooding.